acarney

Sorry this is rushed and sorry I don't have time to play around switching which ICM is connected to which bank, I've been super busy at work (covering two departments since someone is leaving) and I'm hoping you guys can figure out which parts I need so I can order them today in one go and install on Saturday... I really need my car running soon and just have zero time since I'm doing a lot of overtime at work...

I've got some codes I pulled from my 2002 Audi A6 2.7 with ~173k on it. Had a flashing check engine light the other night for a moment and then it went away. Then on the way home from work the next day it began to stutter hard and idle HORRIBLE.

The codes are:

16684 P0300 Random/multiple cylinder: misfire detected

16687 P0303 Cylinder 3: misfire detected

16686 P0302 Cylinder 2: misfire detected

16688 P0304 Cylinder 4: misfire detected

Does that seem like a single ICM died? Both? A single coil? More then one coil?

Hoping to order the right parts in one go so on Saturday I can fix it in one go so I'll have her running for work on Monday. Only other option for parts is dealer, which often is out of parts for the 2.7t... shipping times usually take 2+ days even with expedited service for me so I'm hoping to order before 12pm pacific time today... help guys! Thanks!


(Also, KINDA thinking of buying the coil conversion kit ECS sells, but I would want to get new plugs too... which plugs would you suggest with the kit? What should I gap those too? Should I get the kit, or just stay stock and replace whats broken today? I'm not modded in anyway and usually like to stay stock, but if this improves idle and really is just as "trouble free" as stock then maybe that's what I'll do to replace all coils/ICMs at once... just I really like opening the repair book and being able to find info for my car... this turns it into having to track down internet info... like what gaps the new coils/plugs require... )

johnkk

2 and 3 on passenger side and 4 on driver side. I don't think 3 coils or both ECM's would fail at the same time.

When one ECM fails, I think it is possible for misses to show up on the other side, but I would expect misses on cylinder 1, if passenger bank has failed.

I wonder if you have a vacuum leak or a failing MAF?

Given time issue, I would swap coils around to see if misses move, Probably not, but if so, get new coils.
Check for vacuum leaks with a propane torch(unlit), and if none, then pull the plug on the MAF and see if the missing stops. If it does, I would get a new MAF.

acarney

So I've always heard about the "use propane" to find a vac leak but I don't fully understand how that works... My idea was that it would stumble and almost or totally stall when hit with propane. But, if my car already is idling so rough it seems like it's going to stall, how do I tell when I hit a vac leak. Also, I assume you do this with the engine cold, but what risk do I have with catching something of fire? I'm just really hesitate to use propane when I don't fully understand how it helps find a vac leak... Also, not fully sure where the vac lines run, anyone have a handy replacement how to or guide? Does anyone know how many of what parts I need for a full vac system refresh? (Hate to replace one line & a week later another fails) Can a full system be replaced with "normal tools" (ie no engine lift to reach lines, just normal small item removal or snaking lines...)

I'll try unplugging the MAF when I get home, if it's going bad would that fix the problem as soon as I unplug it? Is that how I tell if it's the issue?

Also, I forgot to mention I think I have an O2 sensor going bad, or fully bad, or something. P1113 I believe is the code. Though I've been told it was bad before about a year ago, had them clear the code and it didn't return till now...

johnkk

If your engine runs rough as soon as you start up from cold, I suspect a vacuum leak.

When propane is drawn into the leak, idle will increase. Won't catch fire even when engine is warm. Carb spray can do the same thing, but I don't like to spray it all over the tubing. The idea is that the propane will find the leak. Just pull the plastic covers off the engine and point the propane at all the hoses on top and around the intake plumbing. If you have a leak, the idle will increase when you find it.

Don't worry about the O2 sensor now. It may have thrown the code again because it doesn't like the fuel mixture caused by other issues.

If the MAF is bad, sometimes the missing will not begin until the engine warms up and goes into "closed loop" operation. Before that, the engine is in "open loop" operation and the MAF is not yet in control, so missing is not apparent. Then when warm and you unplug the MAF, the rough running engine smooths out because the bad MAF is not trying to control the engine. This MAF unplugging is only for testing and just because the idle is better, it doesn't mean that you have fixed the problem and can drive with the MAF unplugged. You will screw up your cat converters without a MAF and have an expensive problem. With a bad MAF, you can unplug to drive a short distance home, but any more than 15-20 minutes and you're pushing your luck.

acarney

Very interesting! I noticed the CEL blinking for about 5 seconds the other night when I was accelerating onto the highway but then it went away. Went to work the next morning (roughly 2 miles) and it was fine. Ran to the doctors office after work (roughly 12 minute drive) and it was fine. Went inside for about 30 minutes and came back out to the car. Started it and it was fine for about 7 or 8 minutes while I sat in it on my phone. Then the idle went crazy +/- 200 rpm or something. Put it in gear and it was bucking. Put it in park and shut it off for about 30 seconds. Start up and rough idle. Eased the baby home on the back roads around 25 mph. It would be almost normal smooth at around 2000rpm but would buck like crazy and flash CEL if I pushed the gas 3/4 way down. Would buck and rpm jump around when at a stop sign. I haven't started it since... I wonder if it'll start ok since its been cold in the garage all day without running... That would point away from vac leak to MAF, correct?

Vac leak should be rough as soon as I turn the engine over cold or hot, yes?

acarney

Had time to play around and some more info. I reset codes and unplugged MAF. Still got misfires on 3 and 4 and of course a MAF code (lol). Cleared and plugged back in but switched my ICM connections, misfire on 3 and 4 still. Since I had the hood up though I could hear what I thought was a hissing sound this time around. It sounds like it's coming from the front top (?) of the engine. Still really uncomfortable using propane around it in the garage and the only stuff I can use is from those blue propane torch bottles which doesn't really have that strong of a stream when not lit. Still I slowly waved it around the throttle body area and there was no difference in the engine sound. Pinching off the two little hoses right near the throttle body would change the pitch or completely stop the hissing sound though. However, I don't think it's either of the little hoses, they look in decent condition and I couldn't feel anything from them, I've taken a little video so you guys can hear the sound difference and hopefully see which area and two hoses I'm talking about.

Does this help track down what/where the leak is? Could it be the throttle body boot? It looks in good condition... could it be the gasket on the TB? It wouldn't be the actual TB would it? OEM is like $1,000 for the stupid part...

johnkk

I think you've found the leak. Pull off the hose that connects to the small vacuum motor and suck on it. I'll bet that it doesn't hold vacuum and the diaphragm is torn in the vacuum motor/valve.

You may also have clogged catalytic converter(s). Fix the vacuum leak first.

Get over your propane fear, and FYI the propane flow is the same whether lit or unlit. The burning jet just makes more noise and seems like more.

acarney

Well then the propane isn't doing anything. Moved it slowly all around those two little hoses that I pinch in the video and nothing happened. Then moved it around the throttle body boot and no change either. Almost positive the hissing sound is coming from that area. I'm over nighting another throttle body boot and gasket (just in case) and I'm hoping I can find the two little hoses locally if I need. I still can't figure out exactly where it would be coming from though. Those little hoses both connect to the same metal "hose" that runs under the intake manifold and back towards the driver rear of the engine. Each one connects to some "bell shaped" device that then connects to one of the plastic intake pipes. The hiss sounds like it's coming from the center, not off to the sides. I would think its the TBB but it actually looks pretty decent... Getting the replacement just in case though so I have something I can try over the weekend at least...

What are those two little hoses connected too?

johnkk

I think the reason the propane showed no leaks is that the problem may be a torn diaphragm in one of your turbo bypass valves. The leak is internal, but still a vacuum leak. Pull the hose off the valve and suck on it, and it probably will not hold a vacuum. Then replace the bad bypass valve and go from there. Actually, you should check both valves to see if they hold vacuum, but I suspect the passenger side is the culprit.

The propane would have detected a leaky throttle body boot, so DFWAB.

acarney

So are those the sort of bell shaped things that those little tiny hoses I was pinching connect to? Happen to have a part number for them? (Is it side specific or would one part fit either side? Might have a family member just pick on up from the dealer today if they have one in stock so I don't have to wait till next week for something to ship... Damn 11 to 12hr work days >.<)